Police discover $1.5 million worth of MDMA powder and pills when responding to a report of a trail of blood. Joe Rosato Jr. reports. (Published Tuesday, Aug. 13, 2013)

A trail of blood led San Francisco police detectives to make one of the biggest drug busts in the department's history, seizing more than $1.5 million worth of MDMA powder and pills.

MDMA is the active ingredient in ecstasy.

The discovery, which came by pure luck, was found the same weekend as the Outside Lands Music & Arts Festival in Golden Gate Park, prompting investigators to wonder whether the drugs were meant to supply concertgoers.

"We're happy if it is just a coincidence," Police Chief Greg Suhr said at a Tuesday news conference. "If it's not, we're very happy that none of this found its way out to the Polo Fields."

Benjamin Hagerl, 36, and Steven Terrell, 31, both of San Francisco, were arrested at about 9:15 a.m. on Sunday in the 3300 block of Mission Street, near 29th Street in the Bernal Heights neighborhood.

Their arrests were made shortly after police responded to a report of possible vandalism and burglary at a building there and found a first-floor window that was broken and stained with blood. The downstairs neighbor had called for help – he told police that a man had broken a window on the first floor when the neighbor wouldn't let him inside the building.

The blood trail led into the building, and police followed it to an apartment inside. That apartment was empty, but the blood trail snaked to another apartment on the second floor.

Officers knocked on the door of the second apartment and police said a man with blood on his hands and pants opened the door, according to police. It turned out to be Hagerl.

Police checked the apartment and found a second man inside, later identified at Terrell, as well as duffel bags containing suspected narcotics.

Investigators eventually determined that there were more than 23 kilograms of MDMA powder and more than 30,000 pills of the drug. Suhr said officers also seized nearly $30,000 in cash and computer equipment.

Hagerl and Terrell were taken into custody on suspicion of possession of controlled substances for sale, maintaining a place for selling or using controlled substances and conspiracy to commit a crime, according to police.

Suhr said Terrell also has a separate drug trafficking case pending in Illinois that involves the sale of marijuana in that state.

In January, federal agents seized 60 pounds of MDMA while the drugs were on their way to San Francisco.